The quantitative distribution of different species ( Q ijklm and H ijklmno) in binary potassium molybdate melts has been investigated by in situ high temperature Raman spectroscopy in conjunction with quantum chemistry (QC) ab initio calculations. The symmetric stretching vibrational wavenumbers of molybdenum nonbridging oxygen bonds in high wavenumber range and their respectively corresponding Raman scattering cross sections were determined and analyzed. Deconvolution of the stretching bands of molybdenum nonbridging oxygen bonds of molten Raman spectra by using the Voigt function was carried out. The six-coordinated molybdenum oxygen octahedra [MoO6]6- have been proposed to be present in molten molybdates, apart from the well-known existence of the four-coordinated [MoO4]2- tetrahedra. The quantitative analysis of different species in the molten K2MoO4-MoO3 system and their dependence on the content of MoO3, as well as the relationship with the viscosities of the melts, were also discussed. The quantitative results have been integrated with published data on physical and chemical properties of the melts.